Current medical treatments have increased the technical demands placed on catheter systems designed for central venous vascular access in patients. The present invention solves a problem that arises as the result of new medical treatment strategies requiring the combined use of certain blood treatment processes such as apheresis and sophisticated supportive care such as autologous bone marrow transplant (BMT).
According to Grishaber, J. E. et al, "Analysis of venous access for therapeutic plasma exchange in patients with neurological disease", J. Clin. Apheresis 7:119-123, 1992, apheresis service (described below) using a central venous catheter is most efficiently done with a dual lumen catheter. Other supportive treatments such as BMT optimally require a triple lumen device, according to Moosa, H. H. et. al., "Complications of indwelling central venous catheters in bone marrow transplant recipients", Surg. Gynecol. Obstet. 172:275-279, 1991. The current choices that a clinician has available are to either use one catheter tyke and thus deliver one phase of therapy inefficiently, or to use two catheters and subject the patient to additional surgical procedures, risks, discomfort and cost.
Apheresis (called also pheresis) is a blood treatment process involving separation of blood elements that can remove soluble compounds or cellular elements from the circulation. Deisseroth et al., "Use of blood and blood products", Cancer: principles and practice of oncology, Devita, V. T. Jr. et al editors, Philadelphia: J. B. Lippincott Company 1989, p. 2045-2059. Blood is withdrawn from a donor, a portion (plasma, leukocytes, platelets, etc) is separated and retained, and the remainder is retransfused to the donor Dorland's illustrated medical dictionary, 27th Edition, W. B. Saunders, Philadelphia, 1988. Specific cell types such as circulating pluripotent stem cells (peripheral stem cells) for use in autologous BMT are harvested using apheresis techniques (leukapheresis).
To pump blood from the patient through the withdrawal lumen, a vacuum must be placed on the withdrawal lumen by a system pump. As the vacuum is increased so as to increase the withdrawal flow rate, the withdrawal lumen tends to collapse. In some cases, this tendency to collapse at low pressures or flow rates prohibits use of a many catheters for apheresis Grishaber et al., supra and Spindler, J. S., "Subclavian vein catheterization for apheresis access", J. Clin. Apheresis 1:202-205, 1983. In contrast, the return lumen is placed under a positive pressure by the system pump to pump blood into the patient, and accordingly, the return lumen is not susceptible to collapse.
Certain prior art tunnelled dual-lumen catheters, such as the Hickman dual lumen catheter, can be used to simultaneously input and output blood to a patient at minimally adequate flow rates. However, these dual-lumen catheters are still susceptible to collapse at more optimal, higher flow rates. Grishaber et al found that additional access was required to complete 27% of procedures when using the Hickman dual lumen catheter and 67% for triple lumen catheters (Arrow International triple-lumen 7 French catheter) and stated in reference to venous access for plasma exchange that they "believe that the difficulties they pose preclude their use for routine procedures." This contributes significantly to the amount of time required to perform these services and increases the cost of these services.
Other dual lumen short-term (non-tunnelled) catheters are larger and stiffer have been designed primarily for dialysis and can accommodate the demands of apheresis. However, these are designed for short-term placement (days to weeks). For example, it is recommended that the dual lumen Mahurkar catheter (Quinton Instrument Company, Seattle, Wash.) be replaced every 3 weeks when used in the subclavian or jugular vein. These catheters are generally recommended for exclusive use for the blood treatment process (see Spindler, supra), and have short stiff external lumen branches that are often uncomfortable and somewhat difficult to dress. Thompson, L., "Central venous access for apheresis access," J. Clin. Apheresis 7:154-157, 1992 and Grishaber, supra. They are therefore not considered satisfactory for longer term general use as for BMT (generally weeks to months). A dual lumen catheter designed for dialysis and long-term use is the PermCath (Quinton). This catheter can sustain the necessary flow rates for apheresis service but is not without problems. This large, stiff, silicone rubber catheter is oval (4.9 mm.times.2.8 mm, OD) and requires a specialized introducer to minimize the risk of air embolism at the time of venous placement. It has a specialized cuff for long term implantation in subcutaneous tissue. It is recommended for internal jugular placement rather than subclavian or external jugular because of the size and stiffness and possibility for complications. Catheter care and comfort thus pose a problem as for similar design short-term dialysis catheters and only 2 lumens are available for general use. Thompson, supra.
BMT is being used increasingly in the supportive care relating to therapy of an increasing array of cancers, including breast cancer. Patients are given intense treatment that is designed to be maximally effective against their cancer with the main toxicity being potentially lethal bone marrow suppression. For autologous BMT, the peripheral stem cells harvested earlier from the patient by apheresis are returned to that patient to repopulate the bone marrow elements depleted by treatment. Patients then require intense supportive care until bone marrow recovery is complete. Optimal vascular access is important for this critical phase of treatment. Current treatment protocols often require administration of multiple drugs and support with intravenous fluids, antibiotics, hyperalimentation, growth factors, and blood products. For efficient administration of these multiple substances, often for many weeks, the use of multiple catheter lumens is optimal. This can be accomplished with dual lumen catheter access systems but is more difficult and requires "juggling" by health care workers of the multiple infusions, medications, and blood draws. Thus. the implantation of catheter systems having three or more lumens is optimal for vascular venous access to facilitate long term intensive medical treatments. Grishaber et. al., supra. For patients undergoing BMT, triple lumen indwelling catheters are generally recommended for vascular access. Moosa et al., supra.
However, for those patients that also require apheresis service, prior art triple-lumen catheters cannot sustain the high flow rates into and out of a patient required for these blood treatment processes and are not recommended for use. The use of a dual lumen Hickman catheter, a tunnelled catheter in common use, is reported but is associated with a significant rate of failure due to failure of the draw port. Even when functional, the flow exchange flow rates are minimal and limiting for this type of catheter and increase the amount of time required to perform an apheresis service and the amount of attention required by personnel administering the service. Another important consideration is that multiple treatments are usually necessary. In order to complete an apheresis blood treatment session in a timely manner, blood must be withdrawn and returned to a patient at an adequate flow rate. For example, stem cell harvest typically requires that nine liters of blood be exchanged in preferably three hours or less. Blood flow rates of 60 cc/min or higher through a catheter are required to provide for such an exchange rate of blood. In addition, the roller pumps in use result in pulsatile flow rather than constant flow and pressures. These relatively high flow rates cannot be approached or sustained by many prior art tunnelled dual lumen catheters in current general use. Applicant is unaware of any tunnelled triple or quadruple lumen catheters that can be used effectively for apheresis. These catheters are soft and flexible with limited internal lumen diameters. The withdrawal lumen used to withdraw blood from the patient is particularly susceptible to collapse.